This paper by Peter Mercelis and Jean-Pierre Kruth investigates residual stresses in selective laser sintering (SLS) and selective laser melting (SLM). The study aims to understand the origin and distribution of these stresses, which can cause part deformations and micro-cracks, limiting the practical use of SLS and SLM parts. The authors develop a simple theoretical model to predict residual stress distributions and use experimental methods to measure these profiles in test samples produced with different process parameters. Key findings include: - Residual stresses are significant in SLM parts, typically consisting of large tensile stresses at the top and bottom, and a large zone of intermediate compressive stress in between. - The magnitude and shape of residual stress profiles are influenced by material properties, sample and substrate height, laser scanning strategy, and heating conditions. - Theoretical and experimental results show that parts remaining connected to their base plate have very high stress levels, while those removed from the base plate have lower stress levels but suffer from deformation during removal. - The exposure strategy, such as line Y or line X scanning, and sector scanning, significantly affect residual stress levels, with stresses being larger perpendicular to the scan direction. - Post-scanning of the part surface with a lower energy level can reduce tensile stress in the upper zone, but full-layer remelting does not significantly reduce residual stresses. - Heating the build platform can reduce residual stress levels, but the effect is limited. The paper provides guidelines to mitigate residual stresses in SLS and SLM processes, emphasizing the importance of understanding and controlling these stresses for better part quality and performance.This paper by Peter Mercelis and Jean-Pierre Kruth investigates residual stresses in selective laser sintering (SLS) and selective laser melting (SLM). The study aims to understand the origin and distribution of these stresses, which can cause part deformations and micro-cracks, limiting the practical use of SLS and SLM parts. The authors develop a simple theoretical model to predict residual stress distributions and use experimental methods to measure these profiles in test samples produced with different process parameters. Key findings include: - Residual stresses are significant in SLM parts, typically consisting of large tensile stresses at the top and bottom, and a large zone of intermediate compressive stress in between. - The magnitude and shape of residual stress profiles are influenced by material properties, sample and substrate height, laser scanning strategy, and heating conditions. - Theoretical and experimental results show that parts remaining connected to their base plate have very high stress levels, while those removed from the base plate have lower stress levels but suffer from deformation during removal. - The exposure strategy, such as line Y or line X scanning, and sector scanning, significantly affect residual stress levels, with stresses being larger perpendicular to the scan direction. - Post-scanning of the part surface with a lower energy level can reduce tensile stress in the upper zone, but full-layer remelting does not significantly reduce residual stresses. - Heating the build platform can reduce residual stress levels, but the effect is limited. The paper provides guidelines to mitigate residual stresses in SLS and SLM processes, emphasizing the importance of understanding and controlling these stresses for better part quality and performance.